Inductors are well-known circuit components that are used to enhance the capabilities of a device. It is also well-known to fabricate inductors of various geometries and shapes on integrated circuit devices.
A preferred shape of inductor that is used in fabricating semiconductor devices is a planar spiral, as is illustrated in FIGS. 1 and 2A and 2B. While a planar spiral shape has advantages, they can be difficult to manufacture. In particular, when using deposition and wet-etching techniques to make inductors, a relatively wide spacing, which leads to a relatively low inductance per unit area, as is shown in the side view of FIG. 2B that is taken along line A-A of FIG. 2A in which there is an inductor 200 that has a width 210 and a spacing 220 which may be greater than 10 um.
It is also known to fabricate multiple inductors on a single integrated circuit chip, as is also shown in FIG. 1A. It is known, for example, to fabricate different inductors 110 and 120 a shown in FIG. 1A on different layers of a semiconductor device, in order to provide multiple inductors. It is also known to fabricate multiple inductors on a single layer, also in order to provide multiple inductors. These multiple inductors can then be interconnected to obtain greater inductance, a greater trace length, matched inductance, and/or other characteristics. While these various configurations have advantages, all suffer from a disadvantage of using a considerable amount of area on the semiconductor chip.
FIG. 1B also illustrates that an interwinding of two inductors is also known, as described in Selmi et al. “Design of an X-band Transformer-Coupled Amplifier with Improved Stability and Layout,” IEEE Journal of Solid-State Circuits, Vol 28, No. 6, June 1993.